Radioactive ignition system



Jan. 5, 1960 w. B. LANE 2,920,238

RADIOACTIVE IGNITION SYSTEM Filed Jan. 18, 1957 IN V EN TOR.

l/ll I 3- Loa g BY I I United States Patent The invention describedherein may be manufactured and used by or for the Government of theUnited States of America for governmental purposes without the paymentof any royalties thereon or therefor.

This invention relates ,to internal combustion engine mounts aradioactive source, such as strontium 90, that emits a plurality ofcollimated beams through a series of spaced holes which usually arearranged to provide one beam for each engine cylinder. Further, a pairof contact points are sealed in an inert atmosphere and are permanentlydisposed in the path of the collimated beams. As may be obvious, in theoperation of such an arrangement the emitted radiation ionizes the inertgas and the circuit of aprimary coil is thereby closed. When the shafthaving the quantity of radionuclide therein, rotates enough so that thebeam passes by the contact points, the gas no longer is ionized andtherefore the circuit of the primary coil is broken. The result of thebreak in the primary coil circuit effects in the usual manner thenecessary induction in the secondary coil for producing the spark across,thegap in an engine plug. Conventional distribution means may beemployed to direct the spark ignition systems and, more particularly, toa battery ignition system having an improved primary current breakingmeans.

Ignition systems of the type almost'universally used with storagebatteries employ an ignition coil formed of primary and secondarywindings for transforming a lowtension battery current to one of highvoltage. Customarily, a set of spring-pressed contacts is mounted in thecircuit to the primary and a breaker or interruptor cam provided with aplurality of cam lobes is used for breaking the contacts andinterrupting the primary current. As is well known, such interruptionscause a sudden decay of flux in the magnetic circuit of the ignitioncoil to produce a high-tension current in the secondary which then iscarried through the distributor rotor to the proper spark plug.

Various breaker or interrupting mechanisms have been into the particularcylinder desired.

The preferred embodiment of the invention is illus trated in the figureof the accompanying drawing, this figure being a diagrammaticillustration of the radioactively ionized ignition system.

i a storage battery 3 which, of course, may be of any suit- Referring tothe figure, certain conventional elements of the conventional breakercam ignition systems are easily recognizable. Thus, the systemillustrated utilizes tor 7. electrically connected to a contact plate 6aby a employed, such as the four-lobe cams with a single breaker arm usedwith the four-cylinder engines, or other interrupters having two sets ofbreaker arms and half as many lobes as there are arms. However, althoughoperation of these mechanisms is satisfactory when the parts are new andproperly adjusted, it frequently is found that the wear on themechanical parts due to friction, arcing, electrolytic erosion and otherphenomena, neces-. sitate constant adjustment and replacement. Further,even under optimum conditions, precise control is not obtainable byadjustment of the contact points because a certain amount of arcing Willbe present between the points. Such arcing introduces unnecessaryresistance into the circuit and ultimately limits the amount of sparkwith resultant deterioration of the combustion characteristics.

It is, therefore, an object of theinvention to provide an ignitionsystem for internal combustion engines which provides good timingcontrol, freedom from arcing and which requires a minimum of adjustmentand maintenance during use.

More specifically, an object is to provide such an ignition system withan interrupter mechanism that employs a minimum of mechanically-movablefriction-producing parts.

A further object of the invention is the provision of an ignition systemwhich reduces the arcing and thereby the introduction of unnecessaryresistance into the ignition circuit.

Broadly considered, these and other objects are achieved by utilizingthe ionizing elfect of radioactive emissions in lieu of the conventionalbreaker arm for interrupting the primary current and initiating thenecessary magnetic flux decay. More specifically, a shaft, which mightbe considered the motor-driven cam shaft,

conductor. 8. Contact plate 65, in turn, is directly connected to thenegative side of the battery and, to reduce the possibility of arcing, aconventional capacitor or condenser 9 also is connected into the primarycircuit in the manner shown.

Secondary winding '5 in which the high-tension, sparkproducing currentis initiated also is electrically coupled to the spark plugs of thecylinders in a somewhat conventional manner. 'Thus, the secondarywinding is connectedby. suitable electric leads to a rotatable arm 11whichisrotatably driven synchronously with the primary current breaking'means subsequently to be de scribed. ,I-I er e again the situation isanalagous to prior ignition systems to the extent the rotatabledistributor arms is driven indirectly by the engine. During itsrotation, arm 11 contacts various points 12 which, in turn, areconnected by electric leads to the various spark plugs (not shown)associated with each cylinder. Such a distributor mechanism, includingarm 11 and contact points 12, is entirely conventional and may assume avariety of types.

One of the principal features of the invention resides in the primarycircuit breaker or interrupting mechanism which, in the presentinstance, includes a source of radioactivity. As may be seen in thedrawings, this interrupter mechanism is in the form of a shaft 16 whichmay be similar in mounting and drive to the conventional breaker camshafts of prior ignition systems. However, in all other respects, bothstructurally and operatively, shaft 16 is a radical departure from theseearlier shafts. In particular, the shaft, which preferably is formed ofsome radiation-shielding material, is provided with a central enclosedchamber in which is mounted a suitable radioactive material 17, such asthe radionuclide strontium which has been found particularly suitablebecause of its half-life characteristics, as Well as the fact 3 that itis a beta emitter eventually decaying into yttrium 90 that has ahalf-life of a few hours. Other radionuclide materials may be usedalthough it is desirable to employ a beta emitter .for reducing healthhazards and for other apparent reasons.

As has been indicated, the purpose of the radioactive material is toform collimated beams which, as shaft 16 rotates, are directed onto theprimary current interrupter contacts 6 and, to permit the formation ofsuch collimated beams, the shaft is provided with a plurality of radialholes or openings 18 spaced in a suitable manner circumferentially aboutit. In the preferred form, there are as many column-forming apertures 18as there are cylinders and the spacing of these columns will bedependent upon rotational speeds as well as the diameter of the shaft.

Another very important feature related directly to the radioactivenature of the interrupter mechanism is the fact that contacts 6 areenclosed in an envelope 19 which is filled with an inert gas such asargon. As a result, as shaft 16 is rotated, each collimated beam in turnsweeps through the gap between the contacts to ionize the gas andtemporarily produce a current flow which, in turn, passes throughprimary winding 4 of the ignition coil to initiate the self-inductionutilized to convert the lowtension battery current into the high-voltagespark. However, when the beam is swung past the contacts so thationization no longer is effected, the primary circuit instantly becomesbroken and the phenomenon of a sudden decay of the flux in the magneticcircuit commences.

Such a decay or sudden decline of the flux produces a high-tensioncurrent in secondary winding 5 which, in turn, is carried to the desiredplug through rotatable arm 11 and one of contact points 12.

From the above description, it will be seen that the radioactiveignitions are utilized for substantially the same purpose as the breakercam to initiate the desired high-tension current. On the other hand, itcan be recognized that the present arrangement utilizes no frictionallyengaged and moving parts such as the lobes of the breaker cams whichcustomarily are employed to physically press apart the contacts for thepurpose of breaking the primary current. For this reason alone, thepresent arrangement is free of such frictional wear as frequentlyproduces arcing or requires constant adjustment or replacement. Also, ascan be appreciated, the gap between contacts 6a and 6b is capable ofbeing precisely fixed as contrasted with the prior gaps which weredependent upon the physical thickness of the breaker cam lobes. Such anability to fix this gap at a predetermined amount is most important tosatisfactory operation and, when the gap is so fixed, it is obvious thatit will not easily be disturbed. Of course, the synchronization of shaftrotation with the move of distribution arm 11 is a matter which willhave to be empirically determined. Also, the size of the apertures, aswell as the length of time involved in ionizing the gas in chamber 19must be specifically determined for each application although suchdetermination should be relatively easily made. Other members, such asthe type of ignition coil utilized, as well as the batteries, theresistances and the capacitors can be developed for individualapplications according to well-known electrical principles. In general,for an automotive ignition system, an ignition coil which has theprimary to secondary turns ratio of between 1:40 to 1:100 in which thesecondary has from 9,000 to 25,000 turns is satisfactory for use with asix-volt system having conventional primary resistances and primaryinductance.

The principal advantage of the present system lies in its elimination ofmechanical wearing parts as well as the fact that parts used areabsolutely susceptible to precise settings and time controls. Obviouslymany modifications and variations of the present invention are possiblein the light of the above teachings. It is, therefore, to be understoodthat within the scope of the appended claims the invention may bepracticed otherwise than as specifically described.

What is claimed is:

1. A device of the type described comprising ignition means, a :firstwinding, a second winding, means for connecting the second winding tosaid ignition means, a power source connected to said first winding,means for containing an ionizable gas, spaced contacts mounted in saidgas containing means, the contacts one connected to said first windingand another to the power source, a rotatable shaft disposed relativelyclose to the contacts, the shaft having a chamber and a plurality ofopenings leading from said chamber to the exterior of the shaft, aradioactive source mounted within the chamber for emanating beamsthrough the openings.

2. An ignition system comprising spark ignition means, a coil having aprimary winding and a secondary winding, means for connecting thesecondary winding to said ignition means, a power source connected tosaid primary winding, an envelope having gas therein, contacts spacedapart and mountedwithin said envelope and connected one to said primarywinding and another to the power source, a rotatable shaft formed with asubstantially closed chamber, and with a plurality of radiallyspacedopenings leading from said chamber to the shaft exterior, and aradioactive source mounted within the chamber for emanating radioactivebeams through said openings, said shaft being so disposed'relative tosaid contacts to cause a beam radiated through said openings to sweepsaid contacts and ionize said gas therebetween, whereby the circuit tosaid primary first is closed and then opened for inducing aspark-producing flux.

References Cited inthe file of this patent UNITED STATES PATENTS

